(1) Field of the Invention
The invention relates to gas turbine engine components, and more particularly to a structural frame comprising an integral fluid reservoir and air/fluid heat exchanger.
(2) Description of the Related Art
In axial-flow gas turbine engines, incoming air is pressurized in a forward compressor section and directed axially rearward through a diffuser to a combustion chamber. In the combustion chamber, fuel is injected into the pressurized air and the resulting fuel/air mixture is burned. Hot combustion gases expand into a rearward turbine section, where energy is extracted, before exiting the gas turbine engine as an exhaust jet.
The turbine section is comprised of alternating axial stages of rotating blades and stationary vanes. The turbine blades transfer the extracted energy to one or more rotor assemblies, which are coupled to the aft ends of one or more central shafts. The shafts extend axially forward and are similarly coupled to one or more compressor rotor assemblies at their fore ends. The shafts are concentric and are supported by bearings mounted within sealed compartments in one or more structural frames of the gas turbine engine.
Pressurized oil is used to lubricate the bearings and to remove heat generated during normal engine operation. The hot oil is directed from the bearing compartments to an oil storage tank and an air/oil heat exchanger before being directed back to the bearings. In most engine configurations, the oil tank is mounted externally to a structural frame surrounding the forward most stage of the compressor, referred to as a fan stage. In other engine configurations, the oil tank is mounted beneath the engine, adjacent to a gearbox. The air/oil heat exchanger uses air from the fan stage to absorb heat from the oil and is also externally mounted. A valve modulates the compressor air to ensure the oil temperature remains within a suitable operating range under all conditions.
In the event of a fan blade or other rotating component failure, it may be possible for an externally mounted oil tank or air/oil heat exchanger to be ruptured by debris. Also, externally mounted oil tanks and air/oil heat exchangers consume a vast amount of space, complicating maintenance of other components. The oil tank, air/oil heat exchanger and associated mounting brackets increase an engine's weight, which reduces the payload carrying capacity and fuel efficiency of an aircraft.
Since aircraft safety is critically important to the aviation industry and the traveling public, any improvement to the safety of a gas turbine engine is desirous. What are needed are an oil tank and air/fluid heat exchanger that are protected in the event of a fan blade or other rotating component failure. Relocation of these critical components from an externally mounted location to a less exposed location will also simplify maintenance and reduce engine weight.